Pilot-operated fluid pressure regulator

ABSTRACT

This invention relates to a pilot-operated fluid pressure control device that includes a main flow control valve and an actuating mechanism for the latter that includes a pilot section and a main section operatively and functionally interconnected by a common pilot control pressure chamber defined between a pair of pressure-responsive means mounted for independent relative reciprocating movement. The pilot section of the actuating mechanism houses one of the pressure-responsive means and it functions as an adjustable spring rest, the equilibrium position of which is determined by the location of an externally adjustable element of a three-element pilot control valve. Fluid pressure within the pilot control pressure chamber counterbalances the biasing force exerted on the pressureresponsive means within the pilot section by a spring, compressible elastic member or other biasing means acting against the opposite face thereof. The other pressure-responsive means is located within the main section with one face exposed to the control pressure in the pilot control pressure chamber and the other to the secondary or delivered pressure. An increase or decrease in the secondary pressure above or below that offset by the control pressure induces a response in the main section pressure-responsive means that closes or opens the main valve operatively connected thereto so that said secondary pressure is returned to and maintained at the preset level thus, once again, restoring equilibrium. An increase or decrease in secondary pressure also acts through the main section pressure-responsive means to bring about a corresponding change in the control pressure and it, in turn, actuates a three-way pilot control valve so as to bleed or add fluid to the pilot control pressure chamber to again establish the equilibrium. If the secondary pressure is still too high after the main flow control valve has closed, the pressure-responsive means within the main section functions as a relief valve to interconnect a controlled pressure chamber and an ambient pressure chamber thus dumping the excess fluid. The control pressure within the pilot control pressure chamber is selectively connected to both atmospheric pressure and the main upstream line pressure through the three-way valve which functions automatically to maintain the control pressure at a preset level.

United States Patent Primary ExaminerLaveme D. Geiger AssistantExaminer-David J. Zobkiw Attorney-Anderson, Spangler & Wymore ABSTRACT:This invention relates to a pilot-operated fluid pressure control devicethat includes a main flow control valve and an actuating mechanism forthe latter that includes a pilot section and a main section operativelyand functionally interconnected by a common pilot control pressurechamber defined between a pair of pressure-responsive means mounted forindependent relative reciprocating movement. The pilot section. of theactuating mechanism houses one of the pressure-responsive means and itfunctions as an adjustable spring rest, the equilibrium position ofwhich is determined by the location of an externally adjustable elementof a three-element pilot control valve. Fluid pressure within the pilotcontrol pressure chamber counterbalances the biasing force exerted onthe pressure-responsive means within the pilot section by a spring,compressible elastic member or other biasing means acting against theopposite face thereof. The other pressureresponsive means is locatedwithin the main section with one face exposed to the control pressure inthe pilot control pressure chamber and the other to the secondary ordelivered pressure. An increase or decrease in the secondary pressureabove or below that offset by the control pressure induces a response inthe main section pressure-responsive means that closes or opens the mainvalve operatively connected thereto so that said secondary pressure isreturned to and maintained at the preset level thus, once again,restoring equilibrium. An

I increase or decrease in secondary pressure also acts through the mainsection pressure-responsive means to bring about a corresponding changein the control pressure and it, in turn, actuates a three-way pilotcontrol valve so as to bleed or add fluid to the pilot control pressurechamber to again establish the equilibrium. If the secondary pressure isstill too high after the main flow control valve has closed, thepressure-responsive means within the main section functions as a reliefvalve to interconnect a controlled pressure chamber and an ambientpressure chamber thus dumping the excess fluid. The control pressurewithin the pilot control pressure chamber is selectively connected toboth atmospheric pressure and the main upstream line pressure throughthe three-way valve which functions automatically to maintain thecontrol pressure at a preset level.

rmmmm 4m 163L878 SHEET 2 0F 3 FIG. 4. JOHN VANDER HORST BY -j WA ArrowPAIENIEBJm 4am 316131.878

SHEET 3 BF 3 INVENTOR j JOHN VANDER HORST BY 40 33 J4 %1% FIG.7.

PILOT-OPERATED FLUID PRESSURE REGULATOR Fluid pressure regulators are,of course, notoriously old in the art as are pilot-operated versionsthereof. The latter fall into two general types, the first of which islittle more than a regulator on a regulator and the second, while stillusing two regulators, interconnects them in such a way that they areinterdependent and one cannot operate without the other. Both types havethe advantages of eliminating the loss of spring load due to the strokeand ease of adjustment because of the lighter spring that can be used.The second or feedback-type pilotoperated regulator has the additionaladvantage of a much better response to fluctuations in flow.

As far as disadvantages are concerned, both types give superiorperformance if a small amount of fluid is bled off the pilot section andexhausted to the atmosphere which, of course, is wasteful and noisy.Also, most existing designs of pilot-operated regulators are exceedinglycomplex and expensive. Probably the most significant disadvantage,however, is one that is shared by virtually all of the prior artpressure regulators and is not, therefore, confined to those of thepilotoperated type, namely, the inability to know in advance what thedelivered pressure is going to be. Even a pressure gauge on thedownstream side of the regulator does not solve this problem as itmerely shows the existing delivered or secondary pressure withoutindicating in advance what it will be.

Since this secondary pressure is of unknown magnitude until it isalready in the line containing the pressure gauge, it constitutes ahazardous condition for both personnel and equipment. The conventionalpractice, therefore, is to turn the regulator all the way off or nearlyso before admitting primary line pressure to the regulator inlet andthen bring the secondary pressure up to the working level slowly whilemonitoring same on the pressure gauge. This, obviously, is atimeconsuming and troublesome operation that could be avoided if onewere able to set and rely upon the regulator to deliver any selectedsecondary pressure. Add to this some means for limiting the setting to apredetermined maximum and one approaches the ideal regulator.

It has now been found in accordance with the teaching of the instantinvention that these and other shortcomings of the prior art regulators,both pilot-operated and otherwise, can be eliminated by adjusting oneelement of a three-way valve such that its location governs themagnitude of the control pressure existing within a pilot controlpressure chamber formed between a pair of pressure-responsive meansmounted for relative reciprocating movement. The control pressureexisting within the pilot control pressure chamber is automaticallymaintained by the three-way valve at a substantially constant levelirrespective of fluctuations in the primary pressure. The secondary orworking pressure is, likewise, maintained substantially constant byinstantaneously compensating for variations in downstream demands. Thestructure of the valve is such that an indicating means connected to theadjustable element of the pilot control valve can be moved in relationto a calibrated dial so as to set the regulator to deliver any desiredsecondary pressure and maintain same with the same degree of accuracy asthat provided by any of the better prior art commercially availableregulators. By being able to preset the delivered pressure, there is nonecessity for turning off the regulator while pressurizing the inlet inorder to protect the downstream equipment from damage. The need for apressure gauge reading the secondary or delivered pressure is, likewise,eliminated.

The construction of the main flow control valve actuating mechanism issuch that the pilot and main sections thereof can either be encased in acommon unitary housing or separated from one another in two differenthousings. In the latter case, a conduit is provided that interconnectsthe two sections of the pilot control pressure chamber found within theseparate housings so as to maintain the same constant control pressurein each.

The constant bleed associated with the better prior art pilotoperatedregulators is eliminated without sacrificing performance and, of course,without wasting fluid. The improved regulator forming the subject matterhereof exhibits a remarkable lack of sensitivity to changes in primarypressure as well as providing a high reverse flow at a very low increasein downstream pressure.

Accordingly, it is the principal object of the present invention toprovide a novel and improved pilot-operated fluid pressure controldevice.

A second objective is the provision of a device of the typeaforementioned which does away with the necessity for providing aconstant bleed while, at the same time, remaining highly sensitive andresponsive to changes in flow.

Another objective of the invention herein disclosed and claimed is toprovide a pressure regulator incorporating means for setting thesecondary pressure at a predetermined value and maintaining this presetlevel substantially constant throughout fluctuating demand patterns andchanges in primary pressure.

Still another object is the provision of a pressure regulator having apressure-responsive control mechanism that includes both a pilot sectionand a main section which can either be encased in a common housing orseparated from one another and functionally interconnected by fluidlines.

An additional object of the invention forming the subject matter hereofis to provide a regulator that gives the user a visual indication ofdelivered pressure without requiring a conventional pressure gauge andat no greater margin of error than that exhibited by the ordinaryindustrial gauge.

Further objects of the invention are to provide a pilotoperated pressureregulator that is compact, rugged, easy to operate, simple toservice'and repair, versatile, readily adaptable to various operatingconditions, relatively inexpensive and even decorative in appearance.

Other objects will be in part apparent and in part pointed outspecifically hereinafter in connection with the description of thedrawings that follows and in which:

FIG. 1 is a diametrical section taken along the common axis of the mainflow control valve and three-way pilot control valve;

FIG. 2 is a horizontal section taken along line 22 of FIG. 1 showing aportion of the two stacked disks broken away to reveal the supportingsurface of the bonnet therebeneath;

FIG. 3 is a fragmentary section to an enlarged scale showing the indexmark and stop on the rotatable indicating means;

FIG. 4 is a fragmentary diametrical section to an enlarged scale showingthe position occupied by the elements of the three-way'pilot controlvalve when the control has dropped below its preset valve;

FIG. 5 is a fragmentary diametrical section similar to FIG. 4 exceptthat the elements of the three-way pilot control valve are shown intheir equilibrium positions indicating that the control pressure is atthe level required to maintain the secondary pressure at its presetvalue;

FIG. 6 is a fragmentary diametrical section similar to FIGS. 4 and 5except that the elements of the three-way pilot control valve are shownin the positions they occupy when the control pressure has risen abovethe level required to keep the secondary pressure at it preset value;and,

FIG. 7 is a diametrical section similar to FIG. I illustrating amodified form of the regulator in which' the pilot and main sections ofthe pressure-responsive valve actuating mechanism are separated from oneanother and housed in difierent casings functionally interconnected byfluid lines.

Referring now to the drawings for a detailed description of the presentinvention and, initially, to FIG. I for this purpose, reference numeral10 has been employed to broadly designate the regulator in its entiretywhich will be seen to include a main flow control valve mechanism and anactuating mechanism for the latter that have been similarly designatedby reference numerals 12 and 14, respectively. In the particular formshown in FIG. 1, the entire valve actuating mechanism 14 is housedwithin the upstanding open-topped cup-shaped walled cavity 16 of thevalve body 18; whereas, in

the modified version of the regulator m shown in FIG. 7, and which willbe described in detail later, the pilot section of mechanism 14 isseparated from the main section 22 thereof and housed in a separate body24.

The main flow control valve mechanism 12 is of conventional design andincludes an inlet 26 defining a primary pressure chamber P" connectableto a source of fluid under pressure and an outlet 28 defining asecondary pressure chamber S" connectable to a service line containingone or more fluid-operated components (not shown) of various wellknowntypes. Intermediate the primary and secondary pressure chambers which,in the particular fonn shown, are arranged coaxially, is located themain valve seat 30 that provides a continuous annular sealing surface 32facing downwardly toward an internally threaded opening 34 in the bottomof the body 18. A removable plug 36 screwed into the opening in thevalve body has an upstanding spring guidepost 38 in the center thereofthat receives one end of compression spring 40. The other or upper endof the spring 40 seats in a recess 42 formed in the underside of valveelement 44 and functions to normally bias the latter into fluidtightsealed engagement with the seat 30. Both the plug and valve element areprovided with the usual O-ring seals 46 as shown.

The shank of a rivet 48 passing upwardly through an opening in the topof the valve element and into the hollow interior of valve stem 50 isused to fasten the latter elements together into a unitary assembly andalso to form an abutment for the upper end of main valve spring 40.Valve stem 50 is mounted for reciprocating movement within an opening 52in the top of valve body 18 where a continuous annular fluidtight sealis formed by O-ring 46 and ring fastener 54. The upper extremity of thestem projects well up into the walled cavity 16 and a downwardlydirected force must be exerted thereon by spring 74 and lower piston 58which comprises the first pressureresponsive means of the valveactuating mechanism 14 of sufficient magnitude to overcome the opposingbias of main valve spring 40. Since rivet 48 has a passage therethroughthat I receives primary pressure through port 60 in the side of thevalve stem and delivers same to the underside of the valve element 44,and the opposed areas acted upon by said primary pressure above andbelow said valve element are essentially equal, any differential forceacross the valve element due to the primary pressure is so small as tobe inconsequential especially when compared with the much greater forceexerted by spring 40. The same thing is true of the secondary pressurebecause the upwardly facing area 62 on top of the valve element 44exposed to said secondary pressure is essentially equal to the opposedarea 64 underneath annular flange 66. Here again, any differential forceacross flange 66 due to the secondary pressure is nonexistent or, atmost, minimal and can be disregarded when compared with the forceexerted by spring 40. Accordingly, it is the force exerted by piston 58on the valve stem 50 that remains the primary factor responsible foropening the main valve and this force is essentially constant regardlessof the fluctuations in primary pressure. The resultant force opposingthe normal bias exerted by valve spring is the sum of the force exertedby spring 74 and the force produced as a function of the differentialpressure across piston 58.

In the particular form shown, the axial opening 70 extending fromend-to-end of the stem 50 is interrupted by an internal annular rib 72that defines an upwardly facing shoulder functioning as an abutment forthe lower end of compression spring 74. The upper end of this samespring engages and biases the second element 76 of the three-way pilotvalve that has been broadly designated by reference numeral 78 upagainst the seat 80 formed on the lower end of the adjustable firstelement 82 thereof. The third element of the three-way pilot valve 78comprises a tubular skirt 84 formed as a part of upper piston 86 whichcomprises the second pressure-responsive means of the valve actuatingmechanism 14 that seats against the frustoconical surface 88 on theupper end of the aforementioned second element 76.

The lower piston or first pressure-responsive means 58 is encircled byan annular rib 90 containing an O-ring groove into which an O-ring sealis fitted that rides in fluidtight sealed contact against cylindricalsurface 92 on the inside of the walled cavity 16. In the particular formshown, piston 58 includes an upstanding annular flange 94 that extendsup inside of a corresponding annular skirt 96 that forms a part ofbonnet 98. The aforementioned flange telescopes loosely inside the skirtso as to normally leave an annular space therebetween. Flange 94provides an annular abutment positioned to engage the O-ring 46encircling the upper piston or second pressureresponsive means so as tohold said O-ring in place during assembly.

At the center of the lower piston or first pressure-responsive means 58is an upstanding tubular hub 100 which fits loosely over the stem 50 andcarries an inwardly projecting annular rib 102 that engages the roundedupper extremity 104 of the latter. It will be readily apparent from anexamination of FIG.

1 that as the lower piston 58 moves downwardly the rib 102 projectingfrom its hub 100 will force the stem 50 down and open the main valve 12so as to pass fluid therethrough. The main valve spring 40 and thepressure in the pilot control pressure chamber 132 oppose one anotherand cooperate to maintain the rib 102 and the rounded end 104 sealeduntil the secondary pressure within the controlled pressure chamber C"is sufficient to raise the lower piston 58 and unseat same from thestern after the main valve has closed thereby dumping fluid from saidcontrolled pressure chamber into the ambient pressure chamber 0 which isat atmospheric pressure.

Now, the outside cylindrical surface 106 of the lower piston hub 100telescopes up into the inner cylindrical surface of a downwardlyextending tubular wall member 108 of the upper piston 86 where an O-ringforms a fluidtight seal therebetween. As illustrated, one wall of theO-ring groove 110 is defined by a removable cap 112 that fits over thefree end of wall 108. The circumferential margin of the upper piston 86carries both an annular rib 114 and shallow skirt 116 that cooperate toretain O-ring 46 in fluidtight sealed contact with the inner cylindricalsurface 118 of the bonnet 98. The underside of the O-ring on the upperpiston need not be retained because the pressure exerted thereon by thefluid in the pilot control pressure chamber acts to continuously bias itup against flange 114.

Bonnet 98 has an inverted generally cup-shaped configuration, thesidewall 120 defining cylindrical sealing surface 118 which is acontinuation of walled cavity 16. The sidewall 120 has an annular rib122 projecting therefrom that rests atop a shoulder 124 provided for thepurpose on the inside of walled cavity 16. This shoulder and theadjoining cylindrical wall surface 126 cooperate with the step 128 inrib 122 to retain an 0- ring which provides a fluidtight sealtherebetween. Surface 126 also includes a snap ring groove adapted toreceive snap ring 130 that holds the bonnet 98 in assembled relationinside the walled cavity 16 of the valve body 18. With the upper pistonin fluidtight sealed relation against the interior cylindrical surface118 of bonnet 98 and the outside surface of the lower piston hub, andboth the lower piston 58 and bonnet making a continuous annularfluidtight seal against the walled cavity 16, these elements cooperatewith one another to define the pilot control pressure chamber 132. Lowerpiston 58 moving in fluidtight sealed relation inside walled cavity 16defines a first piston cylinder type pneumatic servomotor operative tocontrol the main flow control valve and relieve excess pressure in thecontrolled pressure chamber when the latter valve is closed.

A bearing plate 134 has been shown on top of the upper piston 86 and abiasing element in the form of a Belleville washer subassembly 136 islocated between the latter and the top 138 of the bonnet 98 which is inopposed relation thereto. The function of the Belleville washersubassembly is, of course, to urge the upper piston 86 downwardly awayfrom the top 138 of the bonnet, this function being one that can beperformed by many other types of biasing elements. Once again, a

situation exists wherein the upper piston 86 cooperates with the insidecylindrical surface 118 of bonnet wall 120 and Belleville washersubassembly 136 to define a second piston cylinder type pneumaticservomotor functioning in pilot control relation to said firstservomotor. Both of these servomotors operate within the same walledcavity because, functionally, the inside cylindrical surface 118 of thebonnet comprises a continuation of walled cavity 16 of the valve body.

A port 140 in the top of the bonnet is open to the atmosphere andprovides the means for exhausting fluid from the pilot control pressurechamber as it escapes through passage 142 in the hub 144 of the upperpiston, into the annular space 146 between elements 82 and 84 of thethree-way valve 78, and from the latter annular space out into thebiasing element cavity 148 through exhaust port 150 in the upper pistonhub. Ports 150 and 140 are also the means to exhaust excess fluid dumpedfrom the controlled pressure chamber C.

The construction of the upper piston hub 144 is somewhat complex. It hasan axial opening therethrough that loosely accepts element 82 of thethree-way valve and cooperates therewith to define the annular exhaustpassage 146, mentioned previously that opens into ambient pressurechamber O." Third element 84 of the three-way valve 78 is actually anintegrally formed tubular extension of the hub 144 that projectstherebeneath in coaxial relation. The same is true of tubular wallmember 108 which, once again, comprises an integral extension of the hubthat extends downwardly therefrom in radially spaced coaxial relation tothird valve element 84 although considerably longer than the latter. Theannular area of the hub between the aforementioned elements 84 and 108contains the exhaust port 150 which also communicates with the interiorof ambient pressure chamber 0" Annulus 146 opens out into a cylindricalenlargement 152 separated therefrom by a shoulder 154 upon which anO-ring is seated that forms an annular fluidtight seal around theadjustable first valve element 82. The head of valve element 82comprises an elongate threaded portion 156 which rises well above thetop of the upper piston. Its threaded surface does not contactcylindrical enlargement 152 and first valve element 82 can, therefore,move up and down independently of piston 86 and vice versa. 7

A nut 158 is fastened in recessed relation to the underside of thebonnet 98 and the threaded section 156 of valve member 82 is screwedtherein for axially adjustable movement relative to the other twoelements 76 and 84 of the three-way valve 78. Valve member 82 has beenshown provided with a kerf 160 into which a screwdriver is inserted toadjust same axially as will be described in detail presently.

The unique construction of the instant regulator is such that a controlknob and dial subassembly that has been indicated in a general way byreference numeral 162, can be employed to set the delivered pressure atany predetermined value in accordance with a scale calibrated directlyin secondary pressure readings or the equivalent thereof. FIGS. 1-3,inclusive, to which reference will now be made, most clearly reveal thedetails of construction of the aforementioned subassembly 162. Carriedby the bonnet 98 for relative rotational movement about its axis is anexternally flanged member 164 having, in the particular form shown, anaxially disposed hexagonal opening 166 therethrough. A hexagonal nut 168sized to thread onto the threaded section 156 of valve element 82 ismounted within the hexagonal opening 166 for rotational movement withelement 164. A vertically disposed groove 170 on the outside of element164 receives the tongue 172 projecting into the axial opening in controlknob 174, thus interlocking same for conjoint rotation. This controlknob, in the particular form shown, is molded from a suitabletransparent material and carries indexing indicia 176 adjacent its outerperipheral margin visible through the top thereof. A

downwardly extending stop forming rib 178 movable with the therefrom inangularly spaced relation to one another so as to leave a gap 182therebetween (FIG. 2).

Stacked atop the bonnet 98 are a pair of disks 184 and 186, both ofwhich carry ears 188 projecting radially from the peripheral marginthereof. The upper of the two disks 184 has inscribed thereon a scale190 (FIG. 2) thatis calibrated in accordance with the delivered orsecondary pressure existing at any selected rotational position of thecontrol knob. Since the deflection curve for the Belleville washer unitis reasonably close to being linear, the scale markings assume an almostuniform spacing. The scale, once determined, can be used on eachregulator and they need not be separately calibrated to fall well withinthe three percent deviation found acceptable in most industrial pressuregauges. Also, since it takes a force of several hundred pounds todeflect the Belleville washer subassembly only a few thousandths of aninch, less than one complete revolution of the control knob actingthrough adjustable valve element 82 and the upper piston is sufficientto bring about enough deflection thereof to encompass a range ofpressures from atmospheric up to several hundred psi.

The ear or tab 188 on the upper disk is located within the gap 182 leftbetween the fixed stops 180 so as to align the indexing indicia 176 witha particular low reading on the scale which, of course, may be zero inorder to provide a so-called gauge pressure reading or an averageambient pressure to provide an absolute reading. Now, if the secondarypressure can, without damage to downstream equipment or personnel, beoperated at the maximum regulated pressure available at the regulatoroutlet, the ear 188 on the lower disk 186 can either be aligned withthat of the upper disk and placed within gap 182 or located at someother preselected minimum" reading other than zero. If, however, as isoften the case, one wishes to limit the secondary pressure to a levelbelow the maximum available at the outlet of the regulator, then the car188 of the lower disk can be rotated as shown in FIG. 2 ahead ratherthan behind stop forming rib 178 to a point adjacent said selectedlimiting pressure reading on the scale 190 carried by said upper disk.When this is done, the stop 178 on the control knob will strike theadjustable stop formed by the lower disk ear 188 and thus prevent theregulated secondary pressure from being set above a predeterminedlimited value.

The control knob rests atop and turns upon an upstanding annular flange192 formed as a part of bonnet 98. This flange is interrupted at onepoint to provide a gap 194 for the placement of a setscrew 196 that isthreaded into the top of the bonnet. The head of this setscrew is wideenough to project over onto the disks 184 and 186 as shown and providesmeans for releasably fastening same in any selected adjusted positionsuch as that of FIG. 2.

Another unique feature of the control knob and dial subassembly shouldbe mentioned, namely, the ability to rotate the entire subassemblyrelative to the valve body so that scale readings can be placed in anydesired position for easy reading regardless of how the regulator isinstalled. Note in connection with FIGS. 1, 2 and 7 that with controlknob stop 178 abutting the bonnet stop 180 as shown in FIG. 2, thecontrol knob, disks, setscrew, first and third elements of the pilotcontrol valve, Belleville washer subassembly, upper piston, bonnet andother incidental elements associated with the latter can be turnedcounterclockwise relative to the valve body, lower piston, secondelement of the pilot control valve and main valve stem without changingthe functional relationships therebetween at all. With stop 178 againststop 180, the fluid in the pilot control pressure chamber is at ambientpressure so that the above-described elements can turn easily againstsnap ring and the adjacent O-ring.

The kerf of the adjustable valve element 82 is, of course, accessiblethrough the central opening in the top of the control knob. At thispoint, threaded section 156 of valve element 82 can be screwed up ordown in nut 158', however, nut 168 is free to rotate thereon and theposition of this valve element is unaffected by rotation of the controlknob. In order to link up the control knob to the control valve 78, onemust set the indexing indicia carried by the former element to a givendelivered pressure as indicated on scale 190 and, with the regulatorconnected in a high-pressure fluid line, adjust the adjustable valveelement 82 until the secondary pressure available at the regulatoroutlet equals the selected scale pressure as determined by a downstreampressure gauge used for calibrating purposes. A drop of adhesive on thehead of the adjustable valve element will usually suffice to connect itto nut 168 for conjoint rotation and the scale reading can be checkedagainst the actual pressure at a couple of other points beforeconnecting these two elements together permanently. When this is done,the control knob can be removably fastened to the unit by screwing capnut 198 onto the externally threaded upper end of flanged member 164.The control knob can be removed at any time by first unscrewing the capnut in order to have access to the setscrew 196 and disk 186. Of course,once the regulator is set at the factory to deliver the preset pressureshown on the scale, the supplementary pressure gauge is no longer neededexcept, perhaps, for an occasional check on the accuracy of theregulator.

Before turning to the operation of the regulator, it would seem logicalto examine the structure of the modified form thereof shown in FIG. 7and identified by reference numeral 10: because both forms operateexactly the same in all essential respects. The valve body is separatedinto two sections 180 and 18b, thus defining a main regulator sectionindicated broadly by reference letter A connectable into the main fluidline (not shown) and a remotely controlled pilot regulator section B.Valve body section 180 is substantially identical to valve body 18 ofFIG. 1 modification except for a few dimensional changes having nofunctional significance. Section 22 of the modified pressure-responsivevalve actuating mechanism 14m remains unchanged and is located withinvalve body section 18a. The controlled pressure chamber C beneath thelower piston 58m communicates with the secondary pressure chamber S" onthe downstream side of the main flow control valve mechanism 12 by meansof siphon tube 200 which is also found in the FIG. 1 unit. The main flowcontrol valve mechanism 12, islikewise, unchanged; however, instead ofelement 76 of three-way valve 78 emerging from the hollow valve stem 50,a simple solid plug 202 is substituted therefor. Plug 202is sealedinside the hollow core 70 of stem 50 by an O-ring in the same manner asthree-way valve element 76 and is biased upwardly by spring 74a. It isevident from an examination of FIG. 7 that modified bonnet section 98asealed inside walled cavity 160 of valve body section 180 has an opening204 in the top thereof located to loosely receive the upper end of theplug, an overhanging stop forming portion 206 that engages the top ofthe plug to keep it in the stem, and a side opening exhaust port 208allowing fluid which has been dumped from the controlled pressurechamber "C" by the lower piston 58 being raised from its seat 104 on thevalve stem to be exhausted to ambient pressure chamber D" and then intothe atmosphere.

Both sections 180 and 18b of the valve body are provided with cup-shapedwalled cavities identified by reference numerals 16a and 16b,respectively. Walled cavity 16a is, for all practical purposes,identical to walled cavity 16 of the FIG. 1 modification and the lowerpiston 58m and bonnet section 98a occupy the exact same structural andfunctional relationships thereto as the corresponding elements 58 and 98of the previously described regulator unit except for the retention ofthe upper piston O-ring as noted hereafter. Since the upper piston 86 isrelocated in valve body section 18b and is no longer present in section18a, the downwardly extending tubular wall member 108m into whichcylindrical surface 106 of the lower piston hub 100 telescopes is formedas an integral part of bonnet 98aand, for this reason, is stationaryrather than movable as was the case with the corresponding element 108of the upper piston hub. Also, since the lower piston is no longerlocated in valve body 18b, its upstanding annular flange 94 isunavailable to hold the O-ring on the upper piston in place duringassembly.

A port 210 is provided in the top of bonnet section 98a into which isconnected one end of conduit 212, the other end of the latter beingconnected into a corresponding port 214 in the other section of thevalve body 181;. The latter port communicates the interior of the valvebody walled cavity 16b through passage 216. Cap forming section 9811 is,once again, substantially identical to its counterpart 98 of the FIG. 1modification and it is fastened and sealed in fluidtight relation withinwalled cavity 16b of valve body section 18b so as to cooperate therewithand with upper piston 86 to define a fluidtight interior chamber l32b.On the other hand, the lower piston 58m cooperates with the walledcavity 16a of its valve body section 18a and bonnet section 980 todefine fluidtight chamber 132a. Conduit 212 interconnects these twochambers and it cooperates therewith and with passage 216 to define thepilot control pressure chamber which, in the previously describedmodification, was all housed within a single valve body 18.

The only changes worth noting in the pilot section B" are in the valvebody section 16b. An inlet passage 218 connectable to the high-pressureside of the main fluid line (not shown) opens into an axial bore 220which contains spring 74b and second element 76 of the three-way valve78. This spring biases second valve element 76 upwardly into the exactsame functional relationship with elements 82 and 84 of the threewayvalve 78 as was the case with the FIG. 1 modification, the onlydifference being that the valve stem 50 housing same was movable in thelatter unit, whereas, in the instant modification (FIG. 7) the abutmentfor the spring is stationary. Since the lower piston 58 is in the mainsection A" of the regulator, the outer cylindrical surface 106 of itshub 100 is not available to telescope up inside tubular wall member 108of the upper piston and provide a guide therefor. In the FIG. 7modification, this function is performed by upstanding annular guidemember 222, the outer cylindrical surface 224 of which guides and sealsagainst the inner cylindrical surface of wall member 108. In theparticular form shown, annular groove 226 at the base of this guidemember accommodates the lower end of wall 108 and enables the bonnet 16bto be foreshortened slightly so as to make a more compact unit.

Referring next to FIGS. 1, 4, 5 and 6 for a description of the operationof the regulator, it will be assumed that the primary pressure chamberP" is connected to a source of fluid under pressure, a delivery linehaving one or more fluid-consuming tools or the like connected thereinis attached to the secondary pressure chamber S, and the control knob isset at zero" or the equivalent scale reading representing the conditionwhere only ambient pressure exists in the delivery line. Turning thecontrol knob clockwise as viewed from above until the indicating indicia176 is opposite the desired delivered pressure causes adjustable firstvalve element 82 of the three-way valve to move upward a small fractionof an inch from the equilibrium position of FIG. 5 into the positionshown in FIG. 4 as the threaded section 156 thereof turns within nut158. At

this point, of course, hex nut 168 has been soldered, glued,.

brazed or otherwise fastened to the threaded section of first valveelement 82 for conjoint rotation therewith and with the control knob andtubular element 166. As soon as first valve element 82 is screwed upsome portion of one complete turn, its conical end raises away from thefrustoconical seat 88 of second valve element 76 of the three-way valvewhich remains in the same position due to its pressing against the thirdelement 84 which, while movable, has not yet moved. Once first valveelement 82 has moved off second valve element 76, fluid from thehigh-pressure side of the main valve 12 enters the pilot controlpressure chamber 132 by passing through port 60 into the hollow valvestem 50, past spring abutment 72, up through the axial opening inelement 76 and into annular space 146 before finally entering passage142. As the pressure begins to rise in the pilot control pressurechamber 132, the upper and lower pistons 58 and 86 move apart slightly.As piston 58 moves downwardly, annular rib I02 inside the hub thereofwill press down upon the rounded end 104 of the main valve stem 50 andopen the main valve 44 thus allowing fluid to flow into the deliveryline. Siphon tube 200 adjacent the outlet 28 is, of course, admittingthe delivered or secondary pressure from the secondary pressure chamberinto the controlled pressure chamber on the underside of the lowerpiston 58. Meanwhile, the upper piston 86 is being forced upwardly byfluid pressure in the pilot control pressure chamber against the biasexerted on top thereof by Belleville washer subassembly 136. The forcenecessary to compress the Belleville washer subassembly to the pointwhere the three-way valve reestablishes the equilibrium position offirst valve element 82, also determines the delivered pressure because,when this condition exists, no more fluid can enter the pilot controlpressure chamber and the pressure therein remains substantiallyconstant. The lower piston 58 will also have assumed the position shownin FIG. 1 of the drawings shutting off the main flow control valve 12because of the balanced pressure on both sides thereof assuming, ofcourse, no downstream fluid consumption. The secondary pressure existingat this particular adjusted position of first valve element 82 is thatwhich appears by the index mark on pressure scale 190 and the same istrue of all other adjusted positions of this valve element. A conditionnow exists where the main flow control valve has reclosed and thesecondary pressure has risen to the preselected value determined by thesetting of the control knob in relation to the pressure scale 190.

Next, assume that a fluid-consuming load is actuated downstream of theregulator. The secondary pressure will immediately drop and produce apressure differential across lower piston 58 acting in a direction todepress same thus, once again, opening the main valve 12 and supplyingthe downstream demand. As long as the load remains on the line, the mainvalve will stay open to supply same because piston 58 will be occupyinga different equilibrium position lower down in the walled cavity 16.Obviously, as the lower piston drops down slightly due to the lessersecondary pressure therebeneath in the controlled pressure chamber, thecontrol pressure in the pilot control pressure chamber 132 will alsodrop momentarily because of the greater volume between the pistons;however, as soon as the control pressure drops, the Belleville washersubassembly will act to lower the upper piston 86 because the biasingforce of the fluid in the pilot control pressure chamber is no longeradequate to keep this subassembly at the same degree of deflection.Accordingly, the three-way valve has, once again, returned to theposition shown in FIG. 4 where third valve element 84 has moved downcarrying second valve element 76 therewith and away from first valveelement 82 which stays in its same adjusted position. Fluid, therefore,is once again admitted to the pilot control pressure chamber past firstvalve element 82 until the preset pilot control pressure is restoredtherein at the greater volume and the upper piston moves up again to itsformer equilibrium position shown in FIG. 5. Obviously, the only way thepressure in the pilot control pressure chamber can stay constant at itspreset level is to have the lower piston steady in a condition ofequilibrium which means that the secondary pressure is back up to theindicated pressure on the dial setting.

Next, the condition will be examined in which all or part of thedownstream load is taken off the line. An instantaneous increase in thesecondary or delivered pressure will occur which will be communicated tothe underside of lower piston 58 through siphon tube 200 and controlledpressure chamber C that will raise said piston and compress the fluid inthe pilot control pressure chamber until equilibrium is restored at thehigher pressure. The higher pressure in the pilot control pressurechamber will, of course, also raise the upper piston 86 in opposition tothe downwardly directed bias exerted thereon by the Belleville washersubassembly. As the upper piston is elevated, the three-way valve willassume the condition illustrated in FIG. 6 wherein third valve element84 thereof has moved off of the frustoconical surface 88 of chamber 0"out into the atmosphere from the pilot control pressure chamber throughpassage 142, annular space 146, port in the upper piston hub, Bellevillewasher cavity 148, exhaust port 140 in the top of the cap formingelement and finally out underneath the control knob. When the lowerpiston 58 first raised up due to the increase in pressure therebeneath,the main valve will have closed some due to the bias exerted on element44 thereof by compression spring 40 thus diminishing the flow. As soonas the pressure in the pilot control pressure chamber has been restoredto its preset level as detennined by the adjusted position of firstvalve element 82, the three-way valve will have returned to itsequilibrium position shown in FIG. 5 with the upper piston and its thirdvalve member 84 at the preset equilibrium position but with the lowerpiston 58 at a new equilibrium position holding the main valve 12 openthe lesser amount necessary so that the flow therepast will satisfy thediminished downstream requirements and restore the selected secondarypressure to the system.

It should also be noted that, under some circumstances, the suddenremoval of a fluid-consuming load from the line can cause a momentarysurge in secondary pressure to a level which exceeds thatcounterbalanced by the control pressure within the pilot controlpressure chamber. Both the FIG. 1 and FIG. 7 versions of the instantregulator react to the instantaneous back pressures by raising the lowerpiston to the point where the main flow control valve closes and thenfurther until it unseats from the valve stem thus acting as a reliefvalve to dump the excess pressure directly to the atmosphere around thepilot control valve 78 or plug 202 as the case may be. Of course, themomentary upward movement of the lower piston will also bring about acorresponding decrease in the volume and an elevation of the pressure inthe pilot control pressure chamber so as to compress the Bellevillewasher subassembly and bring about the previously described conditionshown in FIG. 6 where the excess pressure is dumped therefrom. Then,once the surge has thus dissipated itself, the opposite condition willexist where both the secondary and control pressure will be below normalthus bringing the FIG. 4 condition into play until equilibrium is againrestored.

Summarizing the above, whenever the conditions in the system are suchthat the secondary pressure is at its preselected value, the three-wayvalve will occupy the equilibrium position of FIG. 5 as will the upperpiston 86 which carries one part of said valve although as previouslynoted the position of the lower piston in relation to the upper willvary with the downstream conditions. At any time the secondary pressurerises above the preselected value, the control pressure in the pilotcontrol pressure chamber will, likewise, rise above its equilibriumvalue causing the threeway valve to assume the FIG. 6 condition untilequilibrium is, once again, restored. Finally, should the secondarypressure fall below the preset value, the three-way valve will respondto this unbalanced condition as in FIG. 4 until equilibrium is againpresent.

It will thus become apparent that whatever factor is responsible forchanging the control pressure in the pilot control pressure chamber,whether it be fluctuations in secondary pressure as the downstream loadvaries or even leakage of fluid from the pilot chamber itself, three-waycontrol valve 78 senses such change and automatically compensatestherefor by either bleeding of fluid in the case of an excessively highpressure or adding fluid to restore it to the preset level. Aspreviously mentioned, the dial scale is calibrated in accordance withthe Belleville washer subassembly or similar biasing means such that thecontrol pressure within the pilot control pressure chamber at any givensetting of adjustable element 82 of the control valve will maintain thedelivered pressure within 3 percent or less of its indicated value.

Finally, with brief reference once again to FIG. 7, it will be apparentthat the three-way valve 78 responds to and controls the pressure in thepilot control pressure chamber in exactly second element 76 thusexhausting fluid into ambient pressure 75 the same way as has just beendescribed in connection with the F IG. 1 modification. The fact that thepilot control chamber is separated into two sections 1320 and 132binterconnected by conduit 212 has no effect on the functioning of theregulator as the pneumatic servomotors that include the upper and lowerpistons respond to fluctuations in control pressure just the same way asif the chamber were a unitary one. The ability to separate the regulatorinto two functionally interconnected sections makes it possible to bringthe control of several regulators located at widely diverse locations toa central control station.

What is claimed is:

l. A regulator for controlling the delivered pressure in a fluid linewhich comprises: a body having a flow passage therethrough that includesan inlet at the upstream end thereof connectable to a source of fluidunder pressure and an outlet at the downstream end adapted forconnection to a fluid-consuming load; main normally closed flow controlvalve means located within the body between the inlet and outletdividing the interior thereof into a primary pressure chamber on theupstream side and a secondary pressure chamber downstream, said valvemeans being operative upon actuation to open and control the flow offluid from said primary pressure chamber into the secondary one; firstservomotor means operative to actuate the flow control valve means inresponse to fluctuations in pressure within the secondary pressurechamber, said first servomotor means including a walled cavity anddefining therein a controlled pressure chamber of variable volume inopen communication with said secondary pressure chamber and a firstpressure-responsive means operatively connected to the flow controlvalve means and mounted for movement within said walled cavity; secondservomotor means operative to control the first servomotor means inresponse to fluctuations in a preset control pressure, said secondservomotor means including a second pressureresponsive means mountedwithin the walled cavity for movement therein relative to the firstpressure-responsive means while cooperating therewith to define a pilotcontrol pressure chamber of variable volume, and biasing meanspreloading said second pressure-responsive means in a direction todecrease the volume in said pilot control pressure chamber; fluidpassage means connected to deliver fluid from the primary pressurechamber to the pilot control pressure chamber and to bleed fluid fromthe pilot control pressure chamber to the exterior of the body; andpilot control valve means associated with the fluid passage means andthe second pressure-responsive means operative to establish andautomatically maintain a control pressure within the pilot controlpressure chamber at a selected preset level, said pilot control valvemeans including a first valve element located in the fluid passage meansand mounted for adjustable movement relative to the secondpressure-responsive means, a second valve element located in the fluidpassage means and normally biased into seated position against saidfirst valve element while cooperating therewith to shut off the supplyof fluid to the pilot control pressure chamber, and a third valveelement located in the fluid passage means for movement with the secondpressure responsive means under the influence of the biasing means intoseated position against said second valve element while cooperatingtherewith to shut off the escape of fluid from the pilot controlpressure chamber, each adjusted position of said first valve elementdefining an equilibrium position wherein a specific control pressure isestablished within the pilot control pressure chamber, the second andthird valve elements cooperating upon a decrease in control pressurebelow the preset value to move as a unit relative to the first valveelement under the influence of the biasing means in the direction toopen the fluid passage means and admit fluid to the pilot controlpressure chamber until equilibrium is restored, and said third valveelement being operative upon an increase in control pressure above thepreset value to move relative to said first and second valve elements inthe direction to oppose the preload bias exerted by the biasing means soas to open the fluid passage means and bleed fluid from the pilotcontrol pressure chamber until equilibrium is restored therein.

2. The fluid pressure regulator as set forth in claim 1 in which: thewalled cavity is divided into three sections, the first forming a partof the body and housing the first pressureresponsive means, the secondbeing separated from the first and housing the second pressureresponsive means, and the third comprising a conduit connected betweensaid first and second sections so as to establish open communicationtherebetween.

3. The fluid pressure regulator as set forth in claim 2 in which: thepilot control valve means is located within the second section of thewalled cavity.

4. .The pressure regulator as set forth in claim 1 in'which:

the body is separated into two sections, the first comprising a mainsection housing the first servomotor means and the second comprising apilot section housing the second pressure-responsive means of the secondservomotor means, the biasing means and the pilot control valve means;and the pilot control pressure chamber comprises cavities within themain and pilot body sections and a conduit interconnecting said main andpilot body section cavities.

5. The fluid pressure regulator as set forth in claim 1 in which: thefirst valve element is rotatably adjustable: indicating means isfastened to the first valve element for rotational movement therewith;and scale means is located and calibrated to cooperate with saidindicating means to provide a visual indication approximating thedelivered pressure corresponding to any preset control pressureestablished by a particular setting of the pilot control valve means.

6. The fluid pressure regulator as set forth in claim 5 in which: theindicating means includes a first stop means movable therewith; and asecond stop means is mounted for movement relative to the scale means,said second stop means cooperating with the first to limit the degree ofrotation of the first valve element in one direction or the other so asto establish a maximum or minimum delivered pressure in each adjustedposition.

7. The fluid pressure regulator as set forth in claim 5 in which: theindicating means includes a first stop means movable therewith; and afixed stop is located in the path of said first stop means, said fixedstop and first stop means cooperating with one another to limit therotation of the first valve element to single revolution.

8. The fluid pressure regulator as set forth in claim 7 in which: thefixed stop means forms a part of the scale means; the scale means isrotatably adjustable relative to the body; and the first stop means isoperative to engage the fixed stop means and rotate the scale relativeto the body upon rotation of the indicating means.

9. The fluid pressure regulator as set forth in claim 8 in which: theindicating means is turned past its lowest scale position in thedirection to decrease the delivered pressure.

10. The fluid pressure regulator as set forth in claim 5 in which: thefirst valve element is threaded so as to provide for axial adjustmentupon rotation, the pitch of said threads being selected to cooperatewith the biasing means so as to define a range of control pressures uponrotation of said first valve ele ment up to one complete revolution.

11. The fluid pressure regulator as set forth in claim 1 in which: thefirst and second pressure-responsive means comprise pistons mounted forrelative reciprocating movement within the walled cavity.

12. The fluid pressure regulator as set forth in claim 1 in which: thefirst and second pressure-responsive means include opposed axiallydirected tubular portions arranged one inside the other for relativetelescoping movement in fluidtight sealed relation, said tubularportions cooperating with one another to define an ambient pressurechamber forming part of the fluid passage means.

13. The fluid pressure regulator as set forth in claim 12 in which: themain flow control valve means includes a valve stem mounted within thewall of the body separating the primary pressure chamber and thecontrolled pressure chamber for reciprocating movement in fluidtightsealed relation thereto; and the first pressure-responsive means isremovably seated against the stern of said flow control valve means soas to cooperate therewith to define a fluidtight seal separating thecontrolled pressure chamber from the ambient pressure chamber, saidfirst pressure-responsive means being operative upon an increase indelivered pressure above the preset value with the main flow controlvalve means closed to unseat from said valve stem and dump the excessfluid into the ambient pressure chamber until said preset pressure isrestored.

14. The fluid pressure regulator as set forth in claim 1 in which: themain flow control valve means includes a valve stem mounted within thewall separating the primary pressure chamber from the controlledpressure chamber for reciprocating movement in fluidtight sealedengagement therewith; the first pressure-responsive means including atubular portion and an apertured seat nonnally resting atop the stem ofthe main flow control valve means in fluidtight sealed engagementtherewith; and the second pressure-responsive includes means attachedthereto, said means including a tubular portion within the pilot controlpressure chamber arranged in fluidtight telescoped relation to thetubular portion of the first pressure-responsive means and cooperatingtherewith to define an ambient pressure chamber open to the atmosphere,said first pressure-responsive means being operative in response to anincrease in pressure within the controlled pres- -sure chamber above apredetermined value to release the main flow control valve into closedposition and unseat from the valve stem so as to dump the excess fluidfrom said controlled pressure chamber into the ambient pressure chamber.

15. The fluid pressure regulator as set forth in claim 1 in which: thethird valve element comprises a tubular member movable with the secondpressure-responsive means, the interior of said tubular member being inopen communication with the interior of the pilot control pressurechamber.

16. The fluid pressure regulator as set forth in claim 1 in which: thebody is separated into two sections, the first comprising a main sectionhousing the first pressure-responsive means and the second housing thesecond pressure-responsive means; the main flow control valve meansincludes a valve stem mounted within the wall separating the primarypressure chamber from the controlled pressure chamber for reciprocatingmovement in fluidtight sealed engagement therewith; the firstpressure-responsive means including a tubular portion and an aperturedseat normally resting atop the stem of the main fluid control valvemeans in fluidtight sealed engagement therewith; the pilot controlpressure chamber comprises cavities within each body section between thepressure-responsive means and a conduit connected therebetween; andmeans within the pilot control pressure chamber in fluidtight sealedattachment to the walled cavity, said means including a tubular portionarranged in fluidtight telescoped relation to the tubular portion of thefirst pressure-responsive means and cooperating therewith to define afirst ambient pressure chamber open to the atmosphere, said firstpressure-responsive means being operative in response to an increase inpressure within the controlled pressure chamber above a predeterminedvalue to release the main flow control valve into closed position andunseat from the valve stem so as to dump the excess fluid from saidcontrolled pressure chamber into the first ambient pressure chamber.

17. The fluid pressure regulator as set forth in claim 16 in which: thepilot control valve means is located within the second body section; thesecond pressure-responsive means includes an inner tubular portiondefining the third valve element and an outer tubular portion encirclingthe inner one; and the second body section has a tubular portioncooperating in telescoped fluidtight relation with the outer tubularportion of the second pressure-responsive means to define a secondambient pressure chamber forming a part of the fluid passage means.

1. A regulator for controlling the delivered pressure in a fluid linewhich comprises: a body having a flow passage therethrough that includesan inlet at the upstream end thereof connectable to a source of fluidunder pressure and an outlet at the downstream end adapted forconnection to a fluid-consuming load; main normally closed flow controlvalve means located within the body between the inlet and outletdividing the interior thereof into a primary pressure chamber on theupstream side and a secondary pressure chamber downstream, said valvemeans being operative upon actuation to open and control the flow offluid from said primary pressure chamber into the secondary one; firstservomotor means operative to actuate the flow control valve means inresponse to fluctuations in pressure within the secondary pressurechamber, said first servomotor means including a walled cavity anddefining therein a controlled pressure chamber of variable volume inopen communication with said secondary pressure chamber and a firstpressure-responsive means operatively connected to the fLow controlvalve means and mounted for movement within said walled cavity; secondservomotor means operative to control the first servomotor means inresponse to fluctuations in a preset control pressure, said secondservomotor means including a second pressure-responsive means mountedwithin the walled cavity for movement therein relative to the firstpressure-responsive means while cooperating therewith to define a pilotcontrol pressure chamber of variable volume, and biasing meanspreloading said second pressure-responsive means in a direction todecrease the volume in said pilot control pressure chamber; fluidpassage means connected to deliver fluid from the primary pressurechamber to the pilot control pressure chamber and to bleed fluid fromthe pilot control pressure chamber to the exterior of the body; andpilot control valve means associated with the fluid passage means andthe second pressure-responsive means operative to establish andautomatically maintain a control pressure within the pilot controlpressure chamber at a selected preset level, said pilot control valvemeans including a first valve element located in the fluid passage meansand mounted for adjustable movement relative to the secondpressure-responsive means, a second valve element located in the fluidpassage means and normally biased into seated position against saidfirst valve element while cooperating therewith to shut off the supplyof fluid to the pilot control pressure chamber, and a third valveelement located in the fluid passage means for movement with the secondpressure responsive means under the influence of the biasing means intoseated position against said second valve element while cooperatingtherewith to shut off the escape of fluid from the pilot controlpressure chamber, each adjusted position of said first valve elementdefining an equilibrium position wherein a specific control pressure isestablished within the pilot control pressure chamber, the second andthird valve elements cooperating upon a decrease in control pressurebelow the preset value to move as a unit relative to the first valveelement under the influence of the biasing means in the direction toopen the fluid passage means and admit fluid to the pilot controlpressure chamber until equilibrium is restored, and said third valveelement being operative upon an increase in control pressure above thepreset value to move relative to said first and second valve elements inthe direction to oppose the preload bias exerted by the biasing means soas to open the fluid passage means and bleed fluid from the pilotcontrol pressure chamber until equilibrium is restored therein.
 2. Thefluid pressure regulator as set forth in claim 1 in which: the walledcavity is divided into three sections, the first forming a part of thebody and housing the first pressure-responsive means, the second beingseparated from the first and housing the second pressure responsivemeans, and the third comprising a conduit connected between said firstand second sections so as to establish open communication therebetween.3. The fluid pressure regulator as set forth in claim 2 in which: thepilot control valve means is located within the second section of thewalled cavity.
 4. The pressure regulator as set forth in claim 1 inwhich: the body is separated into two sections, the first comprising amain section housing the first servomotor means and the secondcomprising a pilot section housing the second pressure-responsive meansof the second servomotor means, the biasing means and the pilot controlvalve means; and the pilot control pressure chamber comprises cavitieswithin the main and pilot body sections and a conduit interconnectingsaid main and pilot body section cavities.
 5. The fluid pressureregulator as set forth in claim 1 in which: the first valve element isrotatably adjustable; indicating means is fastened to the first valveelement for rotational movement therewith; and scale means is locatedand calibrated to cooperatE with said indicating means to provide avisual indication approximating the delivered pressure corresponding toany preset control pressure established by a particular setting of thepilot control valve means.
 6. The fluid pressure regulator as set forthin claim 5 in which: the indicating means includes a first stop meansmovable therewith; and a second stop means is mounted for movementrelative to the scale means, said second stop means cooperating with thefirst to limit the degree of rotation of the first valve element in onedirection or the other so as to establish a maximum or minimum deliveredpressure in each adjusted position.
 7. The fluid pressure regulator asset forth in claim 5 in which: the indicating means includes a firststop means movable therewith; and a fixed stop is located in the path ofsaid first stop means, said fixed stop and first stop means cooperatingwith one another to limit the rotation of the first valve element tosingle revolution.
 8. The fluid pressure regulator as set forth in claim7 in which: the fixed stop means forms a part of the scale means; thescale means is rotatably adjustable relative to the body; and the firststop means is operative to engage the fixed stop means and rotate thescale relative to the body upon rotation of the indicating means.
 9. Thefluid pressure regulator as set forth in claim 8 in which: theindicating means is turned past its lowest scale position in thedirection to decrease the delivered pressure.
 10. The fluid pressureregulator as set forth in claim 5 in which: the first valve element isthreaded so as to provide for axial adjustment upon rotation, the pitchof said threads being selected to cooperate with the biasing means so asto define a range of control pressures upon rotation of said first valveelement up to one complete revolution.
 11. The fluid pressure regulatoras set forth in claim 1 in which: the first and secondpressure-responsive means comprise pistons mounted for relativereciprocating movement within the walled cavity.
 12. The fluid pressureregulator as set forth in claim 1 in which: the first and secondpressure-responsive means include opposed axially directed tubularportions arranged one inside the other for relative telescoping movementin fluidtight sealed relation, said tubular portions cooperating withone another to define an ambient pressure chamber forming part of thefluid passage means.
 13. The fluid pressure regulator as set forth inclaim 12 in which: the main flow control valve means includes a valvestem mounted within the wall of the body separating the primary pressurechamber and the controlled pressure chamber for reciprocating movementin fluidtight sealed relation thereto; and the first pressure-responsivemeans is removably seated against the stem of said flow control valvemeans so as to cooperate therewith to define a fluidtight sealseparating the controlled pressure chamber from the ambient pressurechamber, said first pressure-responsive means being operative upon anincrease in delivered pressure above the preset value with the main flowcontrol valve means closed to unseat from said valve stem and dump theexcess fluid into the ambient pressure chamber until said presetpressure is restored.
 14. The fluid pressure regulator as set forth inclaim 1 in which: the main flow control valve means includes a valvestem mounted within the wall separating the primary pressure chamberfrom the controlled pressure chamber for reciprocating movement influidtight sealed engagement therewith; the first pressure-responsivemeans including a tubular portion and an apertured seat normally restingatop the stem of the main flow control valve means in fluidtight sealedengagement therewith; and the second pressure-responsive includes meansattached thereto, said means including a tubular portion within thepilot control pressure chamber arranged in fluidtight telescopedrelation to the tubular portion of the first pressure-responsive meanSand cooperating therewith to define an ambient pressure chamber open tothe atmosphere, said first pressure-responsive means being operative inresponse to an increase in pressure within the controlled pressurechamber above a predetermined value to release the main flow controlvalve into closed position and unseat from the valve stem so as to dumpthe excess fluid from said controlled pressure chamber into the ambientpressure chamber.
 15. The fluid pressure regulator as set forth in claim1 in which: the third valve element comprises a tubular member movablewith the second pressure-responsive means, the interior of said tubularmember being in open communication with the interior of the pilotcontrol pressure chamber.
 16. The fluid pressure regulator as set forthin claim 1 in which: the body is separated into two sections, the firstcomprising a main section housing the first pressure-responsive meansand the second housing the second pressure-responsive means; the mainflow control valve means includes a valve stem mounted within the wallseparating the primary pressure chamber from the controlled pressurechamber for reciprocating movement in fluidtight sealed engagementtherewith; the first pressure-responsive means including a tubularportion and an apertured seat normally resting atop the stem of the mainfluid control valve means in fluidtight sealed engagement therewith; thepilot control pressure chamber comprises cavities within each bodysection between the pressure-responsive means and a conduit connectedtherebetween; and means within the pilot control pressure chamber influidtight sealed attachment to the walled cavity, said means includinga tubular portion arranged in fluidtight telescoped relation to thetubular portion of the first pressure-responsive means and cooperatingtherewith to define a first ambient pressure chamber open to theatmosphere, said first pressure-responsive means being operative inresponse to an increase in pressure within the controlled pressurechamber above a predetermined value to release the main flow controlvalve into closed position and unseat from the valve stem so as to dumpthe excess fluid from said controlled pressure chamber into the firstambient pressure chamber.
 17. The fluid pressure regulator as set forthin claim 16 in which: the pilot control valve means is located withinthe second body section; the second pressure-responsive means includesan inner tubular portion defining the third valve element and an outertubular portion encircling the inner one; and the second body sectionhas a tubular portion cooperating in telescoped fluidtight relation withthe outer tubular portion of the second pressure-responsive means todefine a second ambient pressure chamber forming a part of the fluidpassage means.